As far as emails go, you can't do much more than track clicks and opens. Often open rates aren't entirely accurate, depending if your provider tracks unique opens only or total opens. I have emails that have been opened over 100 times by the same individual. This isn't accurate at all, it's just their email program fetching the image tracking pixel.
Clicks are a little more accurate as email clients won't trigger it themselves.
Most providers should be able to provide some additional tracking you can put on your site to measure 'conversions' for a given email campaign, but that would have to be via website opt-in. A lot of what goes in at the dealership is over the phone too which isn't going to track automatically anywhere.
Assuming you're using Google Analytics on your site, be sure to tag your links you put in your emails to help you measure/identify that traffic and their behaviour as best you can